1. Field of the Invention
The present invention relates to an optical characteristic analysis method, a sample measuring apparatus and a spectroscopic ellipsometer, with which the optical characteristic of a multilayer film can be analyzed, with voltage being applied thereto, in order to evaluate the electro-optic effect of the material with a multilayer film structure.
2. Description of Related Art
Conventionally, a substance provided with a high-dielectric constant film or a ferroelectric film, formed on a substrate, is used as the material to produce a ferroelectric memory, a ferroelectric capacitor, a piezoelectric element, such an actuator, and an electro-optic device, such as an optical shutter and an optical isolator, and the like. To specify the characteristic of a film of such material is extremely important for influencing the memory performance or the like, and a refractive index, a transmittance and the like change with electric field being applied thereto, known as the electro-optic effect, so for example, the above mentioned features are used in order to evaluate the characteristic of a film.
FIG. 1 is a schematic view showing a conventional measurement method of electro-optic effect. In this measurement method, a pyramidal prism coupling P is placed on the surface of a sample S provided with a film S2 formed on a substrate S1, light is irradiated to the prism coupling P, with required electric field being applied to the sample S, and a refractive index of light, which is projected to the sample S by the prism coupling P, is measured by a required measuring apparatus.
It should be noted that measurement of the electro-optic effect is disclosed also in Japanese Patent Application Laid-Open No. S63-205543 (1988) and Japanese Patent Application Laid-Open No. H1-41838 (1989).
In the conventional measurement method shown in FIG. 1, since a measurement is made with the prism coupling P being placed on the surface of the sample S, there is a problem that a sample S of large size, having a dimension at least sufficient for placing the prism coupling P, needs to be prepared. Moreover, since it is necessary to polish the surface of the sample S, on which the prism coupling P is placed, until a required smoothness is obtained, in order to prevent occurrence of unwanted refraction at the boundary between the prism coupling P and the sample S, there is a problem that preparation of the sample S needs a lot of effort. Furthermore, since a measurement is made for a location where light is projected by the prism coupling P in the conventional measurement method, there is a problem that it becomes extremely difficult to make a so-called in-plane distribution measurement of refractive index for finding out how the refractive index is distributed on the entire surface of the sample S. Moreover, even when the method according to Japanese Patent Application Laid-Open No. S63-205543 (1988) and Japanese Patent Application Laid-Open No. H1-41838 (1989) is used, the in-plane distribution measurement of refractive index, which requires movement of a location of the sample where light is irradiated, needs a lot of effort and time and a measurement cannot be made easily.
On the other hand, when a sample to be measured is a substance provided with a high-dielectric constant film or a ferroelectric film formed on a substrate, it has been reported that an unknown film is automatically formed on the substrate, with the formation of the high-dielectric constant film or the ferroelectric film, and a multilayer film structure (structure having a plurality of layers) is formed as a result. Considering utilization of this substance as the material of a ferroelectric memory, a ferroelectric capacitor or the like, it is extremely important to measure the characteristic of such a multilayer film individually for each layer. A measurement for each layer, however, cannot be made with the conventional measurement method shown in FIG. 1 and, moreover, to measure accurately is difficult even with the method according to Japanese Patent Application Laid-Open No. S63-205543 (1988) and Japanese Patent Application Laid-Open No. H1-41838 (1989).